Data from: Natural selection drives emergent genetic homogeneity in a century-scale experiment with barley

Direct observation is central to our understanding of the process of
adaptation, but evolution is rarely documented in a large, multicellular
organism for more than a few generations. Here, we observe genetic and
phenotypic evolution across a century-scale competition experiment, barley
composite cross II (CCII). CCII was founded in 1929 with tens of thousands
of unique genotypes and has been adapted to local conditions in Davis, CA,
USA for 58 generations. We find that natural selection has massively
reduced genetic diversity leading to a single clonal lineage constituting
most of the population by generation F50. Selection favored alleles
originating from similar climates to that of Davis, and targeted genes
regulating reproductive development, including some of the most
well-characterized barley diversification loci, Vrs1, HvCEN, and Ppd-H1.
We chronicle the dynamic evolution of reproductive timing in the
population and uncover how parallel molecular pathways are targeted by
stabilizing selection to optimize this trait. Our findings point to
selection as the predominant force shaping genomic variation in one of the
world’s oldest ongoing biological experiments.